hi i know only about *.do.
If we declared as *.do then from the browser we give any 
url ends with .do.
ex: http://localhost/8080/../abc.do

Hi Frns.
        In order to achieve MVC architecture feature the 
file should be extends with .do extension. Means if we are 
giving file name as "Login.do" it goes to the mixture of 
MVC architecture.
No idea about do.*.

We can use both. *.do and do.* both are valid in struts. As
a matter of fact anything is valid when we are using the url
mapping. 

*.do or  routes all requests with a .do extension to the
specified page. And in the other case do.* directs all
request urls ending with a do.(html,jsp,whatever)to the
specified page

hey,*.do is the extension match which is vallid in struts.
and /do is the directory match which is also valid,but we
should not mix up both like /do.*/,which is invalid.

If we specify *.do in <url-pattern>, the ActionServlet 
specified in <servlet-class> will respond to all the 
request whicheverr comes from the client.

if we specify do.*, ActionServlet class respond only to the 
request comes from the resource with "do" primaryname and 
with any extension. like do.html, do.jsp, do.do

whatever Tirupathi Rao told it is correct. I am adding few
more words to this question.We need to follow either
extension matching or directory match to achieve "Front
controller" design pattern. By using this design pattern
only we can able to trap all the requests to Action classes
and forwarding control to ActionServlet class.